The rubber compositions utilized in making rubber articles are typically filled with carbon black and/or silica to attain desired physical and chemical characteristics. The interaction between rubber and the filler in such rubber compositions has a profound effect on the physical properties of vulcanizates. In fact, the interaction between the rubber and the filler regulates the degree of dispersion of the filler, the formation of elastomer-filler interface, and the filler-filler network. All of these interactions have a significant effect of the physical properties of the cured rubber composition, such as stress-strain properties, energy loss under cyclic load, abrasion resistance, and tear propagation resistance. Increased polymer filler interaction enables dispersion the filler to a finer degree to achieve a higher level of reinforcement. It also permits the incorporation of higher amounts of the filler and/or for the incorporation of fillers which cannot be properly dispersed into conventional rubbers.
The importance of attaining better rubber/filler interaction has been appreciated for many years and has been the subject of numerous research projects throughout the rubber industry and within academic settings. Attaining improved rubber/filler interaction is of particular interest to manufacturers of rubber products such as tires, hoses, power transmission belts, conveyor belts, windshield wiper blades, and a multitude of other industrial rubber products and consumer goods. One recognized approach for attaining better compatibility between rubbery polymers and fillers is to functionalize the rubbery polymer with moieties that improved interaction with the filler. For instance, rubbery polymers can be functionalized with amines to attain better interaction with carbon black and silica.
U.S. Pat. No. 4,935,471 discloses a process for preparing a polydiene having a high level of affinity for carbon black which comprises reacting a metal terminated polydiene with a capping agent selected from the group consisting of (a) halogenated nitriles having the structural formula X-A-C≡N, wherein X represents a halogen atom and wherein A represents an alkylene group containing from 1 to 20 carbon atoms, (b) heterocyclic aromatic nitrogen containing compounds, and (c) alkyl benzoates. The capping agents disclosed by U.S. Pat. No. 4,935,471 react with metal terminated polydienes and replace the metal with a terminal cyanide group, a heterocyclic aromatic nitrogen containing group or a terminal group which is derived from an alkyl benzoate. For example, if the metal terminated polydiene is capped with a nitrile, it will result in the polydiene chains being terminated with cyanide groups. The use of heterocyclic aromatic nitrogen containing compounds as capping agents can result in the polydiene chains being terminated with a pyrrolyl group, an imidazolyl group, a pyrazolyl group, a pyridyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an indolizinyl group, an isoindolyl group, a 3-H-indolyl group, a cinnolinyl group, a pteridinyl group, a .beta.-carbolinyl group, a perimidinyl group, a phenanthrolinyl group or the like.
U.S. Pat. No. 4,935,471 also discloses that lithium amides are highly preferred initiators because they can be used to prepare polydienes which are terminated with polar groups at both ends of their polymer chains. The extra polar functionality provided by lithium amides results in increased interaction with carbon black resulting in better polymer-carbon black dispersion. The lithium amides disclosed by U.S. Pat. No. 4,935,471 include lithium pyrrolidide. U.S. Pat. No. 4,935,471 also indicates that preferred initiators include amino alkyl lithium compounds of the structural formula:
wherein A represents an alkylene group containing from 1 to 20 carbon atoms, and wherein R1 and R2 can be the same or different and represent alkyl groups containing from 1 to 20 carbon atoms.
It is also desirable for synthetic rubbers to exhibit low levels of hysteresis. This is particularly important in the case of rubbers that are used in tire tread compounds. Such polymers are normally compounded with sulfur, carbon black, accelerators, antidegradants and other desired rubber chemicals and are then subsequently vulcanized or cured into the form of a useful article. It has been established that the physical properties of such cured rubbers depend upon the degree to which the carbon black is homogeneously dispersed throughout the polydiene rubber. This is in turn related to the level of affinity that carbon black has for the rubber. This can be of practical importance in improving the physical characteristics of rubber articles that are made utilizing polydiene rubbers. For example, the rolling resistance and tread wear characteristics of tires can be improved by increasing the affinity of carbon black to the rubbery polymers utilized therein. Therefore, it would be highly desirable to improve the affinity of a given polydiene rubber for carbon black and/or silica. This is because a better dispersion of carbon black throughout polydiene rubbers which are utilized in compounding tire tread compositions results in a lower hysteresis value and consequently tires made therefrom have lower rolling resistance. It is also known that a major source of hysteresis is due to polymer chain ends that are not capable of full elastic recovery. Accordingly, improving the affinity of the rubber chain ends to the filler is extremely important in reducing hysteresis.
U.S. Pat. No. 6,080,835 discloses a functionalized elastomer comprising: a functional group defined by the formula:
where R1 is a selected from the group consisting of a divalent alkylene group, an oxy-alkylene group, an amino alkylene group, and a substituted alkylene group, each group having from about 6 to about 20 carbon atoms, R2 is covalently bonded to the elastomer and is selected from the group consisting of a linear-alkylene group, a branched-alkylene group, and a cyclo-alkylene group, each group having from about 2 to about 20 carbon atoms.
U.S. Pat. No. 5,932,662 discloses a method of preparing a polymer comprising: preparing a solution of one or more anionically polymerizable monomers in a solvent; and, polymerizing under effective conditions, said monomers in the presence of a polymerization initiator having the formula
wherein R1 is a divalent alkylene, an oxy- or amino-alkylene having from 6 to about 20 carbon atoms; and, R2 is a linear-alkylene, branched-alkylene, or cyclo-alkylene having from about 2 to about 20 carbon atoms, Li is a lithium atom bonded directly to a carbon atom of R2; and R3 is a tertiary amino, an alkyl having from about 1 to about 12 carbon atoms; an aryl having from about 6 to about 20 carbon atoms; an alkaryl having from about 7 to about 20 carbon atoms; an alkenyl having from about 2 to about 12 carbon atoms; a cycloalkyl having from about 5 to about 20 carbon atoms; a cycloalkenyl having from about 5 to about 20 carbon atoms; a bicycloalkyl having from about 6 to about 20 carbon atoms; and, a bicycloalkenyl having from about 6 to about 20 carbon atoms; where n is an integer of from 0 to about 10.
U.S. Pat. No. 6,084,025 discloses a functionalized polymer prepared by a process comprising the steps of: preparing a solution of a cyclic amine compound, an organolithium compound, and from 3 to about 300 equivalents, based upon one equivalent of lithium, of a monomer selected from vinyl aromatic monomers, and mixtures thereof, where said cyclic amine compound is defined by the formula:
where R2 is selected from the group consisting of an alkylene, substituted alkylene, bicycloalkane, and oxy- or N-alkylamino-alkylene group having from about 3 to about 16 methylene groups, N is a nitrogen atom, and H is a hydrogen atom, thereby forming a polymerization initiator having the formula A(SOL)yLi, where Li is a lithium atom, SOL is a divalent hydrocarbon group having from 3 to about 300 polymerized monomeric units, y is from 0.5 to about 3, and A is a cyclic amine radical derived from said cyclic amine; charging the solution containing A(SOL)yLi with from about 0.01 to about 2 equivalents per equivalent of lithium of a chelating reagent, and an organic alkali metal compound selected from compounds having the formula R4OM, R5C(O)OM, R6R7NM, and R8SO3M, where R4, R5, R6, R7, and R8 are each selected from alkyls, cycloalkyls, alkenyls, aryls, or phenyls, having from 1 to about 12 carbon atoms; and where M is Na, K, Rb or Cs, and sufficient monomer to form a living polymeric structure; and quenching the living polymeric structure.
U.S. Pat. No. 6,344,538 discloses functionalized monomers and polymerized functionalized monomers selected from the group consisting of 2-(N,N-dimethylaminomethyl)-1,3-butadiene, 2-(N,N-diethylaminomethyl)-1,3-butadiene, 2-(N,N-di-n-propylaminomethyl)-1,3-butadiene, 2-(cyanomethyl)-1,3-butadiene, 2-(aminomethyl)-1,3-butadiene, 2-(hydroxymethyl)-1,3-butadiene, 2-(carboxymethy)-1,3-butadiene, 2-(acetoxymethyl)-1,3-butadiene, 2-(2-alkoxy-2-oxoethyl)-1,3-butadiene, 2,3-bis(cyanomethyl)-1,3-butadiene, 2,3-bis(dialkylaminomethyl)-1,3-butadiene, 2,3-bis(4-ethoxy-4-4-oxobutyl)-1,3-butadiene and 2,3-bis(3-cyanopropyl)-1,3-butadiene, and methods for preparing such functionalized diene monomers and polymers.
U.S. Pat. No. 6,211,321 discloses a diene rubber comprising 40 to 99.99% by weight of combined units of a conjugated diene monomer, 0 to 50% by weight of combined units of an aromatic vinyl monomer, and 0.01 to 20% by weight of combined units of other vinyl monomer comprising at least one of tertiary amino-containing vinyl monomer and halogen-containing vinyl monomer and wherein at least part of said combined other vinyl monomer is quaternized to form quaternized tertiary amino-containing vinyl monomer units, with the provisos that when said other vinyl monomer comprises combined tertiary amino-containing vinyl monomer units it is quaternized with a monohalogenated hydrocarbon and when said other vinyl monomer comprises combined halogen-containing vinyl monomer units it is quaternized with a tertiary amine, and having a Mooney viscosity ML1+4 at 100° C. of 10 to 200, wherein the tertiary amino-containing vinyl monomer is a compound of the formula CH2═CR11A2NR12R13 where R11 is a hydrogen atom or a lower alkyl group, R12 and R13 are each, independently, an alkyl group, an aryl group or an aralkyl group, A2 is an alkylene group, an arylene group, an arylene-alkylene group, an alkylene-arylene group, or a linking group of the general formula —C(═O)-M-R14—, in which M is an oxy group or an NH group, and R14 is an alkylene group, an arylene group, an arylene-alkylene group or an alkylene-arylene group, and R12 or R13 may be combined with A2 to form a heterocyclic ring, and wherein the combined units of the quaternized tertiary amino-containing vinyl monomer have the formula:
where R1 is a hydrogen atom or a lower alkyl group, R2, R3 and R4, are each, independently, an alkyl group, an aryl group or an aralkyl group, A1 is an alkylene group, an arylene group, an arylene-alkylene group, an alkylene-arylene group, or a linking group of the general formula —C(═O)-M-R5—, in which M is an oxy group or an NH group, and R5 is an alkylene group, an arylene group, an arylene-alkylene group or an alkylene-arylene group, and R2 or R3 may be combined with A1 to form a heterocyclic ring, and X is a halogen atom.
U.S. Pat. No. 6,057,397 discloses a silica-containing diene rubber composition that is reported to be superior in resilience (which is an indication of rolling resistance), at least equal, in tensile strength and abrasion resistance, to carbon black-containing diene rubber compositions, and good in processability and hardness characteristics. The silica-containing diene rubber composition disclosed in U.S. Pat. No. 6,057,397 is characterized by containing, as the diene rubber component, a hydroxyl group-containing diene rubber having a weight-average molecular weight of 50,000 or more, or a blend of the hydroxyl group-containing diene rubber and other diene rubber. This composition is produced by a process which uses, as the diene rubber component, a hydroxyl group-containing diene rubber having a weight-average molecular weight of 50,000 or more, or a combination of the hydroxyl group-containing diene rubber and other diene rubber and wherein the mixing of components is conducted by mixing the diene rubber component with at least part of a required amount of silica and then mixing the resulting mixture with the remainder of silica and other compounding agents.
U.S. Pat. No. 6,114,432 is a diene rubber composition comprising 100 parts by weight of a diene rubber component composed of 10 100 weight percent of an amino group-containing diene copolymer rubber (A) having a composition (based on the bound amount) of 40 99.95 weight percent of a conjugated diene monomer, 0.05 20 weight percent of an amino group-containing monomer and 0 55 weight percent of an aromatic vinyl monomer, and 0 90 weight percent of another diene rubber (B), and 10 150 parts by weight of silica having a specific surface area of 50 220 m2/g as determined by nitrogen absorption (BET method), and having excellent heat build-up resistance, tensile properties, abrasion properties and processability, and a preparation method thereof.
U.S. Pat. No. 6,627,721 discloses a rubbery polymer which is comprised of repeat units that are derived from (1) at least one conjugated diolefin monomer, and (2) at least one functionalized monomer having of the structural formula:
wherein R represents an alkyl group containing from 1 to about 10 carbon atoms or a hydrogen atom, and wherein R1 and R2 can be the same or different and represent hydrogen atoms or a moiety selected from the group consisting of
wherein R3 groups can be the same or different and represent alkyl groups containing from 1 to about 10 carbon atoms, aryl groups, allyl groups, and alkyloxy groups of the structural formula —(CH2)y—O—(CH2)z—CH3, wherein Z represents a nitrogen containing heterocyclic compound, wherein R4 represents a member selected from the group consisting of alkyl groups containing from 1 to about 10 carbon atoms, aryl groups, and allyl groups, and wherein n and x represent integers from 1 to about 10, with the proviso that R1 and R2 can not both be hydrogen atoms.
U.S. Pat. No. 7,108,033 discloses a rubbery polymer which is comprised of repeat units that are derived from (1) at least one conjugated diolefin monomer, and (2) at least one leaving group-bearing monomer having the structural formula:
wherein R represents an alkyl group containing from 1 to about 10 carbon atoms or a hydrogen atom, wherein R′ represents a methyl group containing from 1 to about 10 carbon atoms or a hydrogen atom, with the proviso that if R represents an alkyl group then R′ represents a hydrogen atom, wherein R1 and R2 can be the same or different, wherein R1 represents an alkyl group that is functionalized with a leaving group, wherein R2 represents a moiety selected from the group consisting of hydrogen atoms, alkyl groups containing from 1 to 18 carbon atoms, aryl groups containing from 6 to 18 carbon atoms, alkaryl groups containing from 7 to 18 carbon atoms, and alkyl groups that are functionalized with a leaving group.
U.S. Pat. No. 7,108,033 further reveals a tire which is comprised of a generally toroidal-shaped carcass with an outer circumferential tread, two spaced beads, at least one ply extending from bead to bead and sidewalls extending radially from and connecting said tread to said beads, wherein said tread is adapted to be ground-contacting, and wherein said tread is comprised of (I) a filler, and (II) rubbery polymer which is comprised of repeat units that are derived from (1) at least one conjugated diolefin monomer, and (2) at least one monomer having the structural formula:
wherein R represents an alkyl group containing from 1 to about 10 carbon atoms or a hydrogen atom, wherein R′ represents a methyl group or a hydrogen atom, with the proviso that if R represents an alkyl group then R′ represents a hydrogen atom, wherein R1 and R2 can be the same or different, wherein R1 represents an alkyl group that is functionalized with a leaving group, wherein R2 represents a moiety selected from the group consisting of hydrogen atoms, alkyl groups containing from 1 to 18 carbon atoms, aryl groups containing from 6 to 18 carbon atoms, alkaryl groups containing from 7 to 18 carbon atoms, and alkyl groups that are functionalized with a leaving group.